Tube forming method and apparatus

ABSTRACT

A flat strip of metal moving lengthwise first has its edges turned up by roll-forming. Thereafter it moves into the large end of a horn and along one side of the horn so that that side gradually imposes an increasing curvature on the metal and at the exit end of the horn the metal is substantially cylindrical. A non-galling surface is used on the contact face of the horn. A pin between the edges of the sheet at the exit end of the horn orients the cylindrical tube.

Unite States Patent [191 Brunken 5] Mar. 27, 1973 [5 1 TUBE FORMINGMETHOD AND 1,746,281 2 1930 Riemenschneider ..72/176 x APPARATUS 71,187,374 6/1916 Nowak Inventor: a t B en, Medina m. 3,236,083 2/ 1966Lmderoth, Jr. et al ..72/ 176 [73] Assignee: Scientific Tube, Inc.,Addison, 111. Primary Examiner-Milton S. Mehr [22] Filed: June 17 1970Attorney-Darbo, Robertson & Vandenburgh [21] Appl. No.: 46,876 [57]ABSTRACT A flat strip of metal moving lengthwise first has its [52] US.Cl ..72/176, 72/181 edges turned up by roll-forming Thereafter it moves[51] 1151. C]. ..B21d 5/08 into the large end of a horn and along oneside of the Fleld of Search horn so that that side imposes an increasing219/59 curvature on the metal and at the exit end of the horn the metalis substantially cylindrical. A non-galling [56] 7 References C'tedsurface is used on the contact face of the horn. A pin UNITED STATESPATENTS between the edges cf the sheet at the exit end of the hornorients the cylindrical tube. 1,190,351 7/1916 Wilsie ..72/176 3,001,5699/1961 Gradt ..72/ 176 10 Claims, 6 Drawing Figures PATENTFUHARZY m5 sum1 [IF 2 TUBE FORMING METHOD AND APPARATUS BACKGROUND AND SUMMARY OF THEINVENTION A conventional way of manufacturing welded metal tubing is toroll-form a strip of metal into a tubular form and then weld the buttingedges of the strip at the joint. For many purposes this is an emanatelysatisfactory procedure. However, under certain circumstances it isdifficult, if not impossible, to satisfactorily roll-form the strip intoa'cylinder before it is delivered to the welder. For example, aconventional limit is that the diameter of the finished tube must beless than 100 times the wall thickness (i.e., the thickness of the sheetfrom which the wall is made). This limitation becomes particularlysignificant when it is desired to form tubing of relatively thinmaterial. At the same time, there is a substantial commercial demand fortubing having a relatively thin wall. It can, for example, be used inautomobile radiators and other applications where the pressuredifferential across the wall is not particularly great.

Efforts have been made to roll-form this relatively thin metal. It canbe done but it is a slow, laborious process. Lineal speeds arerelatively slow, e.g., about sixty inches per minute. One factor in thisis that the two edges of the cylinder, before welding, will not maintaina constant linear orientation but tend to move back and forth across andat opposite sides of a desired alignment. This requires constantadjustment of the welding apparatus to meet the actual alignment andeven so is likely to result in puckering along the seam.

Another problem that is encountered in the use of conventional practicesis that after welding there is a tendency (particularly with relativelythin wall thicknesses) for the cross section of the tube to assume ateardrop cross-sectional shape, with the weld at the narrow portion ofthe teardrop. In the industry this is referred to as peaking. The stripmaking up the tube is not sufficiently curved, i.e., deformed, duringthe roll-forming operation so that, of its own volition, it willmaintain a cylindrical form. To some extent, the material wants to relaxand resume its original flat configuration and it is the force resultingfrom this relaxing tendency that causes a non-circular configuration ofthe welded tube. Following the present invention, this is avoided and noobservable peaking results in the welded tube.

The principal object of the present invention is to provide a method andapparatus by which even very thin walled material may be quickly andaccurately formed into a cylinder for welding. Furthermore, a constantalignment of the two edges of the material is obtained thus speeding andsimplifying the welding of those two edges together. For example, aprototype of v the invention has operated very satisfactorily at speedsof 170 inches a minute and there is no apparent reason why speeds muchin excess of that cannot be obtained. After welding, the quality of thetubing is so exceptionally good that those skilled in the art areskeptical from looking at the finished product that it could have beenproduced at speeds even. comparable to those conventionally employed.

In this invention the edges of the strip are first curved byroll-forming and the finished forming of the tube is done by confiningthe strip in a horn which has an exit diameter approximately thatdesired for the finished tube.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of an embodiment ofthe invention; a

FIG. 2 is a side elevation of the embodiment of FIG.

FIG. 3 is an enlarged partial perspective view; FIG. 4 is a slightlydifferent partial perspective view; FIG. 5 is a section as seen at line5-5 of FIG. 4 with portions broken away; and

FIG. 6 is a view at line 6--6 of FIG. 2.

DESCRIPTION OF SPECIFIC EMBODIMENT The following disclosure is offeredfor public dissemination in return for the grant of a patent. Althoughit is detailed to ensure adequacy and aid understanding, this is notintended to prejudice that purpose of a patent which is to cover eachnew inventive concept therein no matter how others may later disguise itby variations in form or additions or further improvements. The claimsat the end hereof are intended as the chief aid toward this purpose, asit is these that meet the requirement of pointing out the parts,improvements, or combinations in which the inventive concepts are found.

In addition to a base 11, the disclosed embodiment includes a firstsection, generally 12, for initially bending the edges of a metal strip14, and a second section, generally 13, in the form of a horn forcurling the strip 14 into a generally cylindrical form 15.

The edge forming section 12 comprises two pairs of opposed formingrolls, the first pair comprising rolls 17,

18, and the second pair comprising rolls 19, 20. These rolls aresuitably journaled in the frame portion 21. Rolls 17 and 19 are convexand mate with the respective concave rolls 18 and 20. A pair of guides22 on frame 21 align the strip 14 as it moves into the forming rolls.One or more of these rolls can be connected to a suitable power means 23to provide the driving impetus to move the strip 14 through theapparatus.

The second section 13 can be called a horn. It comprises a solid body 25with a cap 26 at one end and with the two defining a tapered opening 27therethrough.

Opening 27 is relatively large at the entrance end 27a and relativelysmall at the exit end 27b. The diameter of the opening at the exit end27b is only slightly larger than the desired external diameter forthe'finished tubing. An aperture 28 extends along the upper side of thehorn. Extending through the aperture are a plurality of devices forpositioning the strip 14 within the horn opening 27. These comprise fourrollers 30-33 journaled on shafts respectively 34-37. Also, there is ablock 39 having extending ends 40. The ends of the block extend intoslot 41 in body 25. Pins 42 are journaled in ends 40 and are secured tobody 25 so that the block can reciprocate vertically. Springs 43resiliently urge the block upwardly until the ends 40 are in contactwith the heads of pins 42. A second slot 44 also is provided in body 25to receive a corresponding block. In the operation of an actualembodiment it was found necessary only to use one such block positionedin slot 41, and rollers 31, 32 and 33 were omitted.

The interior of opening 27 is provided with a nongalling lining 48, asillustrated in FIG. 5. In the actual prototype this lining was a nylon,which was applied in liquid form and then hardened (a commerciallyavailable practice). The particular nylon employed was Corvel NCA-77,Type 11. Various other plastics known for their hardness and lubricitycould be employed, such as one of the polymerized tetrafluoro-ethyleneplastics such as that sold under the trademark Teflon. It could be ametal, such as a silver plating, often employed for its non-gallingcharacteristics.

In some embodiments it undoubtedly would be possible to do without thenon-galling lining of the horn and perhaps employ liquid lubricant.However, the prototype of the present invention was employed to formthin stainless steel strip 14 into tubing. Even on a hard, polished toolsteel horn the thin stainless steel was scratched to an extent that itswall thickness was reduced by as much as 12 percent. This could not betolerated in the finished tubing. With tubing of other materials andperhaps of greater wall thicknesses what galling there might be couldperhaps be tolerated. The nylon lining was quite effective ineliminating the galling of the stainless steel sheet being formed into atube.

Of course, the purpose of the apparatus is to take a flat strip of metal14 and to turn it into a substantially cylindrical form 15 for movementinto a welder 50. Thus, the two edges 14a and 14b are brought together,or almost together when the sheet is in the cylindrical form so thatthey can thereafter be connected in the welder. In the illustratedembodiment these edges are not brought completely together until afterthey are in the welder. A pin 51 is positioned between the edges 14a and14b at the exit opening 27b of the horn. This pin is secured to the cap26 and serves to accurately fix the orientation of the edges 14a and 14bin their rotational position about the axis of the tube so that they arealways in the same place. This greatly facilitates and speeds up thewelding operation to have the seam always at a particular location aboutthe axis of the tube, in addition to resulting in a better finishedproduct.

The strip 14 is driven through the apparatus by any suitable means. Asthe flat strip enters the machine the guides 22 serve to accuratelyalign the strip with respect to the forming rolls 17-20. The two pair ofrolls bend the strip 14, particularly in the areas adjacent the twoedges 14a and 14b into a curved configuration. See particularly FIGS. 3,4 and 5. This is very important, not only to provide proper movement ofthe strip through the born, but also with respect to avoiding peaking ofthe welded tube. Thereafter, the strip moves through the horn and as itdoes so it gradually acquires additional curvature corresponding to thecurvature of the interior of the horn until it is substantially circularin cross section at the exit opening 27b. The rolls 30-33 are employedfor the purpose of forcing the strip 14 to conform to the interiorconfiguration of the horn. They bear against the face 140 and urge face14d into immediate juxtaposition with the face of the horn about opening27. As already mentioned, it has been found with the prototype operatedon thin stainless steel to be necessary to use only a single roll 30.The block 39 has a rounded bottom edge which is positioned just abovethe line traversed by the two sheet edges 14a 14b when the sheet iscentered in the bottom of the horn. Should the sheet 14 tend to curl toone side, i.e., no longer be centered at the bottom of the horn, therespective edge 14a or 14b will contact the bottom of block 39 andprevent the sheet from shifting very far out of its proper position atthe bottom of the horn.

Within limits a single set-up can be employed for different diameters oftubing, merely by changing the cap 26 and adjusting the guides 22. Thus,for example, were a tube 15 to be formed of slightly smaller diameter, astrip 14 having a width between edges 14a and 14b proportionatelysmaller would be employed. The guides 22 would be adjusted in width toconform to the sides of the new sheet. A different cap 26 having anopening 27b of the desired diameter would be substituted for that usedin the set-up illustrated. Using this revised setup the substitutedsheet 14 would be formed into a tube 15 having the slightly smallerdiameter. The limits within which this can be achieved are determined bythe necessity of the rolls 17-20 to significantly curl the edge areas ofthe sheet and the avoidance of too great a taper in that portion of theopening 27 lying within cap 26.

The horn should be sufficiently long to result in a gradual bending ofthe edge-curved strip into the finished cylindrical form. An effort tocause an abrupt transition in this respect will result in difficulties.To avoid this, the horn should have a length substantially greater thanthe width of the strip to be formed, i.e., at

least several times the width of the strip.

I claim:

1. A method of forming an elongated flat strip of metal having opposedfaces between two edges substantially into an elongated cylinder, saidmethod comprising the steps of:

moving said strip lengthwise along a path;

at a first location along said path roll forming the edge portions ofthe strip in curves out of the plane of the strip and in the samegeneral direction therefrom with the curves of the edge portions beinggreater than the curve of the part of the strip between the edgeportions, thereby forming a concave face and a convex face; and

along a subsequent length of said path, which length is at least severaltimes the width of said strip, continuously contacting the convex faceof said strip and forcing said strip gradually into cylindrical form asit moves through said length.

2. A method as set forth in claim 1, wherein the contact over saidlength is made by a comparatively rigid non-metallic material.

3. A method as set forth in claim 2, including the step of applying aforce against the concave face in the direction of said one side of saidpath.

4. In an apparatus for forming an elongated flat strip of metal havingopposed faces between two edges and moving along a path substantiallyinto an elongated cylinder of a given diameter, the improvement whereinmeans for bending the portions of the strip adjacent the edges intocurves out of the plane of the strip with the curves of the edgeportions being greater than the curve of the part of the strip betweenthe edge portions thereby forming a concave face and a convex face;

the subsequent component being in the form of a horn having a relativelyflat curvature at the entrance end and an exit end of approximately saidgiven diameter, means on the interior of said horn defining anon-galling surface.

5. In an apparatus as set forth in claim 4, wherein said means definingsaid non-galling surface is a plastic facing.

6. In an apparatus as set forth in claim 5, wherein the convex face ofsaid strip contacts a side of said horn between said ends,

and including pressure means between said ends for contacting said stripand applying a force against said strip in the direction of said side.

7. In an apparatus as set forth in claim 6, wherein said pressure meansis a roller which contacts the concave face of the strip.

8. In an apparatus as set forth in claim 6, wherein said pressure meansis a transverse bar which contacts one or the other edges of the stripdepending upon the orientation of the strip in the horn.

9. In an apparatus as set forth in claim 4, wherein, at a location at oradjacent said exit end an orientation pin is positioned between theedges of the strip.

10. In an apparatus as set forth'in claim 4, wherein the convex face ofsaid strip contacts a side of said horn

1. A method of forming an elongated flat strip of metal having opposedfaces between two edges substantially into an elongated cylinder, saidmethod comprising the steps of: moving said strip lengthwise along apath; at a first location along said path roll forming the edge portionsof the strip in curves out of the plane of the strip and in the samegeneral direction therefrom with the curves of the edge portions beinggreater than the curve of the part of the strip between the edgeportions, thereby forming a concave face and a convex face; and along asubsequent length of said path, which length is at least several timesthe width of said strip, continuously contacting the convex face of saidstrip and forcing said strip gradually into cylindrical form as it movesthrough said length.
 2. A method as set forth in claim 1, wherein thecontact over said length is made by a comparatively rigid non-metallicmaterial.
 3. A method as set forth in claim 2, including the step ofapplying a force against the concave face in the direction of said oneside of said path.
 4. In an apparatus for forming an elongated flatstrip of metal having opposed faces between two edges and moving along apath substantially into an elongated cylinder of a given diameter, theimprovement wherein said apparatus comprises: two components positionedsequentially along said path; the first of said components beingroll-forming means for bending the portions of the strip adjacent theedges into curves out of the plane of the strip with the curves of theedge portions being greater than the curve of the part of the stripbetween the edge portions thereby forming a concave face and a convexface; the subsequent component being in the form of a horn having arelatively flat curvature at the entrance end and an exit end ofapproximately said given diameter, means on the interior of said horndefining a non-galling surface.
 5. In an apparatus as set forth in claim4, wherein said means defining said non-galling surface is a plasticfacing.
 6. In an apparatus as set forth in claim 5, wherein the convexface of said strip contacts a side of said horn between said ends, andincluding pressure means between said ends for contacting said strip andapplying a force against said strip in the direction of said side.
 7. Inan apparatus as set forth in claim 6, wherein said pressure means is aroller which contacts the concave face of the strip.
 8. In an apparatusas set forth in claim 6, wherein said pressure means is a transverse barwhich contacts one or the other edges of the strip depending upon theorientation of the strip in the horn.
 9. In an apparatus as set forth inclaim 4, wherein, at a location at or adjacent said exit end anorientation pin is positioned between the edges of the strip.
 10. In anapparatus as set forth in claim 4, wherein the convex face of said stripcontacts a side of said horn between said ends, and including pressuremeans between said ends for contacting said strip and applying a forceagainst said strip in the direction of said side.